The present invention relates to a display device, and more particularly to a lateral-electric-field liquid crystal display device which exhibits an excellent field-of-view characteristic and high reliability.
In a liquid crystal display device, a TFT substrate on which pixels each of which includes a pixel electrode, a thin film transistor (TFT) and the like are formed in a matrix array and a counter substrate which faces the TFT substrate in an opposed manner and on which color filters are formed at positions corresponding to the pixel electrodes on the TFT substrate are arranged, and liquid crystal is sandwiched between the TFT substrate and the counter substrate. In the liquid crystal display device, an image is formed by controlling optical transmissivity of liquid crystal molecules for every pixel.
The liquid crystal display device is flat and lightweight and hence, the application of the liquid crystal display device has been spreading in various fields. A miniaturized liquid crystal display device has been popularly used in mobile phones, DSCs (Digital Still Cameras) and the like. A field-of-view characteristic is important in the liquid crystal display device. The field-of-view characteristic is a phenomenon in which the brightness changes or chromaticity changes between a case where a screen of the liquid crystal display device is viewed from a front side and a case where the screen of the liquid crystal display device is viewed from an oblique direction. An IPS (In Plane Switching) method which operates liquid crystal molecules by a horizontal electric field exhibits the excellent field-of-view characteristic.
Although various IPS methods are known, for example, there has been known a method in which a common electrode is formed in a matted manner in plane and a comb-teeth pixel electrode is arranged above the common electrode with an insulation film sandwiched therebetween, and liquid crystal molecules are rotated by an electric field generated between the pixel electrode and the common electrode. Since this method can increase the optical transmissivity, this method has been used as a mainstream currently. A liquid crystal display device which adopts such a method is disclosed in JP-A-2007-328210 (patent document 1), for example.